I hate welding ... - Cast Aluminium Pulse-Jet

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pezman
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I hate welding ... - Cast Aluminium Pulse-Jet

Post by pezman » Mon May 09, 2005 8:07 pm

Actually, I just wanted to get some attention. I am hoping to make a cast aluminum PJ -- at least the prototype will be cast. The reason is that the it would be hard to torture steel into the shapes I'm envisioning. I am confident that I can cast the required shapes w/o too much problem, though.

I am aware that normal pulsating combustion would burn the aluminum, but I plan to run this at a reduced duty cycle. The hope is that it will spend most of its time idle and will be substantially cooler than a normal pj.

I guess that I have several questions:

How hot can I reasonably run an Al structure? If it is pulsing, say, 1/6 as often as a normal pj of equivalent size and has heat fins, will it stay cool enough? I am going to guess "yes" on that one, since dynajets have aluminum heads.

Is it just the heat that gets you when you use aluminum or will direct exposure to combustion kill it for another reason? The 1971 Vega comes to mind ... My guess is that it will hold up well enough for a PJ.

Is coating the aluminum (e.g. with SS sleves or ceramic coatings) a possibility? I really like the idea of ceramic coating and the prices actually seem pretty sane: http://www.performancecoatings.com/prices.html . An otherwise conventional coated aluminum PJ might actually be a cheap way to build them as long as it is durable enough.

BTW, this a valveless just in case it has any bearing on the answers ...

Edited title and fixed link for you lol. Tom

pezman
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re: I hate welding ... - Cast Aluminium Pulse-Jet

Post by pezman » Mon May 09, 2005 10:54 pm

I guess I'd rather not go into too much detail about how I propose to reduce the duty cycle, but you are right -- it is not a normal engine design and that's part of the reason that it would be hard to fabricate in the normal way. Plus I hate fabrication anyway -- the idea of pouring stuff into a mold and having something beautiful come out is very appealing.

I think that I'll try bare aluminum for the first crack at it. I'm pretty sure that it will survive long enough to tell me a thing or two.

I got the idea for ceramic coating when I was watching an episode of American Chopper. I would imagine that inside coatings are subject to pretty severe conditions (vibration, heat, rapid changes in temperature etc.) and the parts that are actually in the engine get even rougher treatment. It would be cool if they actually provide enough protection for aluminum PJs -- it could spark a revolution in design.

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re: I hate welding ... - Cast Aluminium Pulse-Jet

Post by pezman » Mon May 09, 2005 11:56 pm

I was thinking more along the lines of lost foam ...

Mark
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re: I hate welding ... - Cast Aluminium Pulse-Jet

Post by Mark » Mon May 09, 2005 11:58 pm

If you go with copper tubing, you could have a higher melting temperature by about 700 F and a beautiful blue-green color. Those little copper atoms are keen when excited, not as pretty as clouds of violet iodine vapor, but close. My brother had a girlfriend who said it was the prettiest color she had ever seen, if you like that blue/green sort of thing. Copper will emit some vivid colors with a swirly flame combustion toy. I guess there are many colors that can evoke such feelings. I remember Oliver Sacks said he had some color that affected him so, causing other senses to come into play, if you have ever experienced that associative sort of thing.
As an aside, I was reading one of his books entitled, "An Anthropologist on Mars", yet not anywhere in the book was there any reference to what an eerie trick he played upon his readers. I set the book down and was going to drift off to sleep, and I was startled by the fact that he had made the cover of his book glow in the dark. Imagine reading some haunting perception of the brain and then being provoked by a glow in the dark book cover. Very sly. He was also a consultant for the movie Rain Man. I remember seeing Dustin Hoffman backstage at the Riviera where I worked, he came to see the show "Splash" when he was in town for the filming of that movie. Another good book by Oliver Sacks is "The Man Who Mistook His Wife for a Hat." And too there is the book "The Island of the Colorblind." What was interesting to me was the cycad plant which was responsible for the afflictions from eating the plant, it has motile gametes, a plant that propels DNA with cilia, just like humans. And funny it was the way all plants did it originally, before they perfected the seed which could live without water. Imagine the first scientist to watch a "plant" cell moving about ala locomotion, the wonder he might have experienced. Who would have thought flagella would have fallen by the wayside during the dinosaurs or some later point, the seed a better method of reproduction for plants. All in all, the neurologist Oliver Sacks out of Harvard is an interesting read. The only other time I can remember being startled by a glow in the dark phenomenon is when I was camping high in the mountains of Oregon with my girlfriend. Just before zipping up the tent in the dark I noticed a stunning beam of light shining out of a hole in the ground near the tent. It was a bioluminescent bacteria or fungi that had taken up residence in some moist woody matter. I chipped and wrapped the glow in the dark fungi or bacteria living in the wood in a wet paper towel and it lived at least a week when I got home, you could cup your hands around it and see the glow. And now I return you to your regularly scheduled program.
1984 F. compared to 1220 F. (Copper vs. Aluminum melting points).
Mark
http://members.cox.net/kaiotea/audio.htm
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re: I hate welding ... - Cast Aluminium Pulse-Jet

Post by Mark » Tue May 10, 2005 2:00 am

Activated carbon as a capacitor.
Mark
http://www.intel.com/capital/cases/cap-XX_print.htm
PS This should have been posted under a tidbit, as it is nothing more.
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re: I hate welding ... - Cast Aluminium Pulse-Jet

Post by steve » Tue May 10, 2005 2:13 am

I've seen the fungi mark was talking about, really amazing stuff! look at wet partially rotten wood at night and you might find some. I believe its sometimes called foxfire.
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